Color photography



Sept 18, 1951 H. VON FRAUNHFER ET Al. 2,568,208-

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Patented Sept. 18, 1951 OFFICE coLoR PHo'rocRArHY Hans Von Fraunhofer, Finchley,London,andA Harry Edward Coote, Londonh England ApplicatioirMarchiZ, 1947, Serial No. 137,992 In Great Britain February 1,71947l 2 Claims.

This invention relates to a process of colour vphotography in which the sensitive materials employed are of the chromogenic integral' monopack type.

Processes using such materials have great practicalA advantages; over processes of other types. Only a single exposure in a standard type of camera is required and the subsequent printing and processing operations can be carried out in normally equipped laboratories. However, the processes of this general type which are' now in use requirehighly skilled and costly handling at each step toV avoid the many pitfalls inherent in this type of process and the general object of the present invention is to provide a process of the type referred to which is relatively simple andv inexpensive to operate in commercial scale production.

All the colour photograph processes using chromogenic integral monopack materials which are now in commercial use employ a three colour analysis and synthesis. Accordingly, the sensitive material employed comprises a Celluloid or other base and ve superimposed coating layers, namely three layers of emulsion separated from each other by two lter layers of gelatine. The productionl of such material requires five separate coating operations and the productive capacity ofi any givenv coating plant is correspondingly reduced.

Moreoven great practical diiliculties are experienced in practice in providing three properly matched, colour formers. The colour balance or the material can be badly affected by small differences in the concentration ofthe coupling components. in thel three emulsion layers or by small diierences in the temperature at which the various layers are coated. Furthermore, the colour balance of any ve layer chromogenic` material may easily be so upset as to ruinr the negative or print by small variations in the composition, temperature and age, of the solutions used in processing the material.

In the process of the presenty invention, these diil'iculties and` disadvantages-are largely avoided or overcome by the use of sensitive material having only two emulsion layers. The particular object of the present invention', therefore, is the provision of a colour photography process, employing material of the chromogenic integral monopack type, which permits the; production. of truly natural colour prints or positives from. a two colour analysis negative..

In the process of the invention, a twoemulsion.

positive material, comprising an, emulsion layer 2 containing a magenta colour former superimposed on an emulsion layer containing a bluegreen colour former, is printed onto from a two colour analysis negative in such manner that an image corresponding to the red-yellow colour values is formed in the emulsion layer containing the magenta colour former and an image corresponding tothe blue-green colour values is formed in the emulsion layer containing the blue-green colour former, and thev emulsion layer containing the magenta coloured image isv then treated with a colour rectifier solution which selectively deposits yellow in the silver image.

A The operation and advantages of the method of the invention will bestbe understood from the following description of a specific embodiment thereof, the details of which are, of course, given by way of illustration only and not by way of limitation. Reference may be had to the accompanying drawing which indicates the course of the colouring process by means of briefed flow diagram.

I -n this particular process, we employ a neg-ative material comprising a carrier or base coated successively with a red Sensitive emulsion layer containing a magenta colour former, a, yellow filter layer and a blue-green sensitive emulsion layer containing a blue-green colour former.

A two emulsion material of this type is far simpler and considerably less expensive to produce than a three emulsion material with two filter layers, nor is its` production nearly as critical as thel latter material because adjustment in printing and processing for slight diierences between the coating weights of the two layers of `emulsion is far simpler than. is the adjustment of corresponding diierences in the case of the three emulsion material. Moreover, While the choice of: the three. colour forming substances is of critical importance in a live-layer material, we find that wev can use any two colours in our negative material so long as they are widely separated from each other, or can be widely separated from each other by the use of a suitable printing lter;

r After exposure we develop and process our above described negative lm in the following manner: The negative is rlrst passed through a developing solution which is made up as follows:

SodumSulphite 9% ozs.

Water to 2Q. gallons The normal developing time varies between 10 to 15 minutes and, thereafter the lm is passed through a stop and clearing bath which is made up as follows:

Pounds Sodium Bisulphite 2 Sodium Acetate '7 Water to 20 gallons After passing the film through the above solution for two to three minutes, it is passed into a xing bath made up as follows: y

Pounds Chrome Alum 21/2 Sodium Hydrosulphite 40 Water to 20 gallons The negative remains in the bleaching solution for approximately 6 to 3 minutes; thereafter it is washed in a cascade washing tank for to 7 minutes, then passed into a fixing bath made up as stated above for 5 to 6 minutes; thereafter it is washed again and then dried.

The nished negative iilm is printed through a suitable iilter of greenish-yellow colour which converts the magenta colour of the one layer into a red colour and the blue-green colour of the other layer into agreen colour, in a single exposure on to a special positive material. This positive material comprises a carrier or base coated successively with an orthochromatic layer of emulsion containing a blue-green colour forming substance and a red sensitive layer of emulsion containing a magenta colour forming substance.

rl`he exposed positive film is passed through a colour rectifier solution of aceto-acetanilide or acetacet 2,5 dichloroanilide, made up by dissolving 11/2 ozs. of the dye in 60 ozs. of alcohol, and thereafter the .lm is developed and processed in the same manner and in the same solutions as prescribed for the negative film. Alternatively, the acetoacetanilide rectiiier may be mixed into the developing solution or, in the case of a two tank developingI procedure, it may be mixed into either the first or the second tank, depending upon the results desired in the nal print.

The result of this treatment with the colour rectiier is that the lower layer of the positive lm, carrying the blue-green coloured image, is not affected by the rectifier to any extent, whereas the top layer, carrying the magenta coloured image, receives a suiicient selective deposit of yellow in the silver image to produce a range of colours from deep red to yellow which, in combination with the lower blue-green coloured image results in a truly natural colour rendering in the positive or print.

It will be appreciated that the process above described is extremely simple and is easily handled and controlled in commercial scale production. An additional advantage of our above described procedure of making natural colour lms or photographs is in the fact that We obtain considerably sharper images than -is possible to ob- 4 tain by a ve-layer material because of the fewer separating layers present in our negative and positive lms.

We claim:

1. Process for preparing natural colour prints on positive photographic material having only two light sensitive silver halide emulsion layers containing dyestuff components superimposed on a base layer, said dyestuif components being capable of forming a dye in the places of the silver picture upon being contacted with a colour forming developer, said process comprising forming in one layer of `an integral bipack colour separation negative a magenta image recording red from a natural subject, forming in the other layer of said negative -a blue green image recording blue green from said subject, exposing said positive through the formed negative and through a greenish yellow filter, said positive material having a red sensitive silver halide emulsion layer, containing a magenta dyestui component coated on a base and an orthochromatic sensitive layer containing a blue green dyestuff component superimposed on said red sensitive layer, developing the exposed positive material and causing colour coupling of the dyestuff components to take place therein whereby a magenta image is formed of the negative record of the natural red and a blue green image is formed of the negative record of the natural blue green, and forming a selective yellow deposit on the silver image in the magenta coloured layer of the exposed positive whereby a range of colours from deep red to yellow is formed in the magenta coloured layer of said positive which in combination with the blue green coloured image in the outer layer of the positive will result in a natural rendition of the colours of the subject.

2. Process for obtaining the effect of a threecolour photographic rendition of a natural subject having red, blue, green, and yellow colours by employing a negative element and a positive element, each of which elements includes only two light-sensitive silver halide emulsion layers, said process comprising exposing the negative element from an emulsion side to light from said subject, said negative element having respectively coated onto a base layer a red-sensitive silver halide emulsion layer containing a magenta dyestuif component, a yellow filter layer, and a blue greensensitive layer containing a blue green dyestuif component, whereby the red of the subject is recorded in the red-sensitive layer and the blue green of the subject is recorded in the blue greensensitive layer, accomplishing development and color coupling of the dyestuff components in said negative producing a magenta image of the red record and a blue green image of the blue green record, exposing the positive element through a greenish yellow Iilter and the developed negative, said positive element having superimposed on a base layer an orthochromatic silver halide emulsion layer containing a blue green dyestuff component and a red-sensitive silver halide emulsion layer containing a magenta dyestuff component, whereby the red record of the subject carried by the magenta image of the negative is recorded as an image in the red-sensitive layer of the positive and the blue green record of the subject carried by the blue green image of the negative is recorded as an image in the orthochromatic layer of the positive, accomplishing development and color coupling of the dyestul components of and within the exposed positive producing a magenta image of the red record and a blue green image of the blue green record, and forming a selective yellow deposit on the silver image in the magenta Coloured layer of the positive whereby a range of colours from deep red to yellow is formed 5 in the magenta coloured layer of said positive which in combination with the blue green eolcured image in the outer layer of the positive will result in a natural `rendition of the colours of the subject. 10

HANS VON FRAUNHOFER. HARRY EDWARD COO-TEi REFERENCES CITED The following references are of record in the 15 file of this patent:

Number Number UNITED STATES PATENTS Name Date Hernandez-Mejia Mar. 7, 1916 Crespinel Oct. 8, 1935 Gaspar Jan. 21, 1936 Combes Mar. 28, 1939 Eggert et al. Aug. 13, 1940 Verkinderen Aug. 12, 1941 Wilmanns et al Jan. 6, 1942 FOREIGN PATENTS Country Date Great Britain July 27, 1936 

1. PROCESS FOR PREPARING NATURAL COLOUR PRINTS ON POSITIVE PHOTOGRAPHIC MATERIAL HAVING ONLY TWO LIGHTS SENSITIVE SILVER HALIDE EMULSION, LAYERS CONTAINING DYESTUFF COMPONENTS SUPERIMPOSED ON A BASE LAYER, SAID DYESTUFF COMPONENTS BEING CAPABLE OF FORMING A DYE IN THE PLACES OF THE SILVER PICTURE UPON BEING CONTACTED WITH A COLOUR FORMING DEVELOPER, SAID PROCESS COMPRISING FORMING IN ONE LAYER OF AN INTEGRAL BIPACK COLOUR SEPARATION NEGATIVE A MAGENTA IMAGE RECORDING RED FROM A NATURAL SUBJECT, FORMING IN THE OTHER LAYER OF SAID NEGATIVE A BLUE GREEN IAMGE RECORDING BLUE GREEN FROM SAID SUBJECT, EXPOSING SAID POSITIVE THROUGH THE FORMED NEGATIVE AND THROUGH A GREENISH YELLOW FILTER, SAID POSITIVE MATERIAL HAVING A RED SENSITIVE SILVER, HALIDE EMULSION LAYER CONTAINING A MAGENTA DYESTUFF COMPONENT COATED ON A BASE AND ON ORTHOCHROMATIC SENSITIVE LAYER CONTAINING A BLUE GREEN DYESTUFF COMPONENT SUPERIMPOSED ON SAID RED SENSITIVE LAYER, DEVELOPING THE EXPOSED POSITIVE MATERIAL AND CAUSING COLOUR COUPLING OF THE DYESTUFF COMPONENTS TO TAKE PLACE THEREIN WHEREBY A MAGENTA IMAGE IS FORMED OF THE NEGATIVE RECORD OF THE NATURAL RED AND A BLUE GREEN IMAGE IS FORMED OF THE NEGATIVE RECORD OF THE NATURAL BLUE GREEN, AND FORMING A SELECTIVE YELLOW DEPOSIT ON THE SILVER IMAGE IN THE MAGENTA COLOURED LAYER OF THE EXPOSED POSITIVE WHEREBY A RANGE OF COLOURS FROM DEEP RED TO YELLOW IS FORMED IN THE MAGENTA COLOURED LAYER OF SAID POSITIVE WHICH IN COMBINATION WITH THE BLUE GREEN COLOURED IMAGE IN THE OUTER LAYER OF THE POSITIVE WILL RESULT IN A NATURAL RENDITION OF THE COLOURS OF THE SUBJECT. 